The "Real" Number of Washington State Adolescents Using Marijuana, and Why: A Misclassification Analysis.

Background: Although causality is difficult to establish, the regular use of marijuana has been associated with many adverse physiological and sociological consequences. There is considerable concern regarding marijuana use among adolescents, as the likelihood of adverse consequences increases significantly for this age group. The most comprehensive data for identifying risk factors for adolescent marijuana use is typically self-report, which may be over- or under-reported for a variety of reasons, including stigmatization, peer-pressure, or fear of being discovered.

Objectives: To identify the prevalence of adolescent marijuana use in Washington State, and the associated risk and protective factors, while controlling for and estimating the extent of misreporting, and its determinants.

Method: Data came from the 2014 Washington State Healthy Youth Survey. We accounted for missingness using chained multivariate imputation equations, resulting in 33,320 complete observations. Our model was estimated using a maximum likelihood multiple regression designed to control for systematic misclassification in binary dependent variables.

Results: Approximately 12% of Washington adolescents claimed to have used marijuana in the past 30 days. Our estimates indicate this figure is likely closer to 18%. Determinants of use included use of other substances, gender, age, and measures of deviant social influences, personality/attitude, school and family bonds, bullying, and acquisition ease. Determinants of misreporting included use of other substances, gender, parental education, and family bonds.

Conclusions: Failing to control for misreporting considerably underestimates the prevalence of marijuana use among adolescents. Our model allows us to better identify at-risk adolescents and inform focused prevention efforts.